Shimano XTR Disc Brake B-M975 L/R
Shimano’s cross-country ﬂagship brake is lovely to look at, superbly priced and comes with some unique options, but weight is less racey than you’d expect.
We like it a lot, but its power, while reasonable by the standards of lightweight cross-country brakes, is low in comparison with everything else out there. Magura's Marta, for example, whups it on power and it's a lot lighter.
We’ve also found that it’s prone to excessive lever travel after assembly, even after multiple bleeds.
Nevertheless, once you’ve knocked it into shape the XTR brake’s twin pistons give powerful, precise braking and trouble-free functioning.
The light single-piece forged body is small, neat and simple to fit. The minimalist forged two-finger lever, with a small mineral oil reservoir as part of the clamp, offers great control and comfort for most fingers though a few testers found the angular shape didn’t suit them and made modulation awkward.
Light and easy-to-fit hose lines emerge from the reservoir at 45 degrees for tidy routing and the lever reach is easily adjusted.
Plenty of options
Shimano were late coming into the highly competitive disc brake market, but these days you'll see the new XTR brake on both cross-country and downhill rigs.
The brakes come in kit form, because there are several options, depending on whether you like to use a Dual Control set-up or separate brake levers and Rapidfire pods. Each lever kit contains hoses and mineral oil.
The calliper is available to fit either international standard and post mount fork bosses to help keep the weight down. With adapters, it can be used with 140, 160, 180 or 203mm rotors, although a standard calliper fits a 160 rotor.
The titanium back plates on the pads are said to be very stable under high temperatures and our experience to date is that the resin pads are far harder wearing than previous Shimano versions. Sintered pads are also included for use in wet conditions.
The rotor is excellent. We really like the fitting and removal simplicity of Shimano's Centre Lock system; the big alloy spider is a super stiff and very light support for the rotor; and the braking surface is heat-treated stainless steel designed to assist pad clearing in mud and cooling under load.
Get the bleed right
Bleeding is a simple process - well, relatively simple - but needs to be performed a few times during initial set-up because there seem to be more places than usual for air to hide.
The trick is to make sure the callipers are as far below the reservoirs as possible so that gravity can help, and a bleed kit is included.
Beating the lines Basil Fawlty style with a stick to remove bubbles, and bleeding it with the pads out and the pistons against the rotor to back pressure the system and reduce excessive lever feel is what most shop mechanics we've talked to recommend.
We've done about 400km off road so far on our test set and, apart from the fact that we had to bleed the rear brake four times and the front twice in the first few days, they've been pretty much trouble free.
The complete system weight for our 160mm rotor set came in at 730g a pair. Most of the weight saving against Deore XT via the DUal COntrol units (about 90g saving for only £20 more).
Looking at all the obvious weight-saving cut-outs, we’re surprised at how heavy this is compared to other flagship cross-country brakes. There’s no denying that the XTR discs are a bargain price for high kudos kit, though.